1. Field of the Invention
This invention relates generally to computer networking and, more particularly, to the design of media access control (MAC) filtering on Ethernet physical layer (PHY).
2. Description of the Related Art
Various interface standards for connecting computers and external peripherals are in wide use today, each aiming to provide simple connectivity at high speeds. Examples of such standards include the IEEE (Institute of Electrical and Electronics Engineers) 1394 standard also referred to as FireWire, and the Universal Serial Bus (USB), both high-speed serial bus protocols. The most widely used networking standard for connecting computers in both Local Area Networks (LANs) and Wide Area Networks (WANs) has been the Ethernet protocol. More specifically, Ethernet is the IEEE 802.3 series standard, originally based on the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) method that provided a means for two or more computer stations to share a common cabling system. CSMA/CD has formed the basis for Ethernet systems that reached transfer speeds in the megabit range, that is the Mbit/sec range. Recent switched based and/or router based Ethernet systems are capable of supporting transfer rates in the Gbit/sec range. Ethernet generally makes efficient use of shared resources, is typically easy to reconfigure and maintain, and provides compatibility across many manufacturers and systems, while keeping the cost low.
The Ethernet defines a number of wiring and signaling standards for the physical layer (PHY), through means of network access at the Media Access Control (MAC)/Data Link Layer, and through a common addressing format. Above the PHY, Ethernet enabled devices typically communicate by transmitting data packets, which comprise blocks of data that are individually sent and delivered. As with other IEEE 802 LANs, each Ethernet station is given a single 48-bit MAC address, which is used both to specify the destination and the source of each data packet. The MAC data communication protocol sub-layer is a sub-layer of the data link layer specified in the seven-layer OSI (Open System Interconnect) model (layer 2), and acts as an interface between the Logical Link Control (LLC) sub-layer and the network's physical layer. It emulates a full-duplex logical communication channel in a multipoint network to provide addressing and channel access control mechanisms that make it possible for several terminals or network nodes to communicate within a multipoint network, typically a LAN or a WAN.
Wake-on-LAN (WOL) is an Ethernet-based computer networking standard developed to turn on or wake up computers through a network packet. The wake up packet is typically transmitted by a program that is executed on another computer on the same LAN. In case the awakened computer is communicating via Wi-Fi, a supplementary standard called Wake on Wireless LAN (WoWLAN) is employed to remotely wake up the computer. The WOL and WoWLAN standards are often supplemented by vendors to provide protocol-transparent on-demand services. WOL support is typically implemented on the motherboard (e.g. in the BIOS) of a computer and the network interface (firmware), and is therefore operating system independent. Some operating systems, however, can control WOL behaviour via hardware drivers. Motherboards with an embedded Ethernet controller that supports WOL do not require cable connections, but if the network interface is a plug-in card rather than an integrated feature on the motherboard, the plug-in card may need to be connected to the motherboard by a cable.
WOL is implemented by transmitting a special packet referred to as “a magic packet” uniquely defined for the purpose of waking up the computer. The magic packet contains the MAC address of the destination computer, which the listening computer can identify to recognize that a magic packet is addressed to it. Upon receipt of the magic packet and having recognized the MAC address, the destination computer initiates system wake-up. The magic packet is sent on the data link layer and broadcast to all network interface controllers (NICs), which may be separate interface cards or may be built in on the motherboard, using the network broadcast address. Hence, the WOL feature is platform-independent. In order for WOL to work properly, at least certain portions of the network interface circuitry are required to remain turned on in order to detect a magic packet, thereby consuming standby power. If WOL is not required, disabling it may reduce power consumption slightly while the computer is switched off but remains plugged into power.
The magic packet is typically a broadcast frame containing six bytes all having a value of 255 (FFFFFFFFFFFF in hexadecimal) anywhere within its payload, followed by sixteen repetitions of the target computer's 48-bit MAC address. Since the magic packet is only scanned for the above string, and not parsed by a full protocol stack, it may be sent as any network-layer and transport-layer protocol. Magic packets are typically sent as UDP datagrams to port 7 or port 9, but they may be targeting any of the available ports. Standard magic packets require a destination computer MAC address, they do not provide a delivery confirmation, they may not work outside the LAN, and they may require hardware support of WOL on the destination computer, as the WOL implementation is designed to be simple and is intended for quick processing by the NIC circuitry, with minimal power requirement. Since WOL operates below the protocol layer, the MAC address is required, and WOL may not be performed using IP addresses and/or DNS names.
Other corresponding issues related to the prior art will become apparent to one skilled in the art after comparing such prior art with the present invention as described herein.